Are search engines considered AI?
I believe it would be more accurate to say that (some) search engines use AI.  Broadly saying "search engines are AI" is not really correct. At the core, most search engines are nothing more than an inverted text index using something like tf–idf scoring. That's a very mechanical/simple thing that nobody would really call AI. 

But more sophisticated search engines may use AI or AI techniques to do things like semantic analysis - so they can actually "answer questions" instead of just looking up words in an index.